Event Update Fourth Quarter 2012

1. Event UpdateFourth Quarter 2012 February 26, 2013 Board of Directors Meeting

2. 4th Quarter 2012 Events 4th Quarter 2012 Event and Compliance Monitoring Report

3. 2012 Events 4th Quarter 2012 Event and Compliance Monitoring Report

4. NERC Event Category Examples • Category 1 - unexpected loss of 3 or more BPS elements contrary to design; failure or misoperation of SPS/RAS; unplanned evacuation from BPS control center facility with BPS SCADA for 30 minutes or more; loss of generation of 1000-1300 MW in ERCOT Interconnection; etc.* • Category 2 - loss of all BPS control center voice or SCADA, control, or monitoring functionality for 30 minutes or more; unintended loss of 300 MW or more firm load for > 15 minutes; loss of off-site power to nuclear generating station, violation of IROL for > Tv; unintended system separation resulting in island of 1000-4999 MW, etc.* • Category 3 - loss of 1,400 MW or more in ERCOT Interconnection or unintended system separation resulting in an island of 5,000 MW to 10,000 MW* • Category 4 - loss of load or generation from 5,001 MW to 9,999 MW, or unintended separation resulting in an island of more than 10,000 MW* • Category 5 - loss of load or generation of 10,000 MW or more* • Category 0 -events below the above thresholds, such as SPS activations, useful for trending purposes. 4th Quarter 2012 Event and Compliance Monitoring Report